Film sound recording system



E. C. MANDERFELD FILM SOUND RECORDING SYSTEM March 10, 1942.

Filed Nov. 21, 1939 REDUCTION SPEECH RIBBON REDUC TIOIV RIBBON NOISE N 0 U8 mm R FIG. 4

"NOISE REDUCTION RIBBON SPE E C RIBBON INVENTOR E, c. MANDERFELD i- WF ATTORNEY NOISE REDUC.

by the valve of Fig. 3;

Patented Mar. 10, 1942 i Emanuel C. Manderfeld, Los Angeles, Calif., a's-.

slgnor to Western Electric Company, Incor-' porated, a corporation of New York Application November-21, 1939, Serial No. 305,441 7 2 Claims. (01. 179-1003) This invention relates to film sound recording systems, and particularly to the production of a multiple, unilateral variable width 'film sound record by means of a ribbon light valve.

The object of the invention is to record sound with a ribbon light valve as a plurality of unilateral variable width film records.

A feature of the'invention' is a recording system including a ribbon light valve having a plurality of ribbons, certain of the ribbons being oscillated in accordance with the signal currents. and the other ribbons being-moved in accordance with the envelope of the signal currents.

Another feature of the invention is a lightvalve having a plurality of recording apertures. displaced in the direction of motion of the film. and having their nearest edges in alignment.

A further feature of the invention is the location of the light valve ribbons with their longitudinal axes at an angle to the axes of-the recording apertures. In the drawing:

Fig. l diagrammatically shows an optical system embodying the invention:

Fig. 2 is a fragmentary-view of an element of the system shown in Fig. 1;

'Fig. 3 discloses a. two-ribbon bodying the invention;

Fig. 4 shows a negative sound record produced Fig. 5 discloses a four-ribbon light valve embodying the invention;

Fig. 6 shows a negative sound record by the valve of Fig. 5; and

Fig. 'l diagrammatically shows the elements of a sound recording circuit associated with the light valve. I

Referring to Fig. 1, light from the light source I is projected by means of the condensing lens system 2 upon the lens system 1 mounted in the pole-pieces of a ribbon light valve 4. The light from the light valve 4 is projected by an objective lens system 5 upon a photographic film I, moved at constant speed by known driving means (not shown);

The light valve'l may be of the general type shown in British Patent 479,083, accepted Januproduced ary 31, 1938, on a communication bythe assignee of the present application. and corresponding in part to the copending U. S. application Serial .No. 140,598, filed May 4. 1931by J. G. Frayne. assigned to the assignee of the present application. While this light valve is mentioned for convenience by way of illustration of a typeof light valve suitable for use in the present syslight valve emtem, the invention is not limited to this type of light valve and many changes" may be made in the details and construction of the light valve within the scope of the present invention.

Fig. 3 diagrammatically illustrates a twostring light valve of the type disclosed in British Patent 479,083, modified in accordance with the present invention. The apertures I, I are displaced from each other, thedisplacement being such that, as viewed from the film, the displacement appears to be in the direction of motion of the film. In many cases, this displacement will actually be in a vertical direction, but optical means may easily be inserted in the optical system so that an actualhorizontal displacement is converted into a virtual displacement in the direction of motion of the film. Theleft edge of the aperture 1 is aligned with the right edge of the aperture 8. The ribbons I, III are inclined to the axes of the apertures I, 0. The degree of inclination will depend upon the permissible displacement at full modulation of the ribbons. The ribbons are shown inclined at an angle of about 75 degrees, but this angle may be reduced to 45 degrees or less. The apertures I, 8 may be formed in the pole-pieces of the light valve, or may be formed in an opaque member supported in a larger aperture in the pole-pieces currents, such as a radio receiver, a phonograph 1 pick-up, etc., may be substituted for the microphone li asdesired. The signal currents are suitably amplified in the amplifier l4 and supplied to the .ribbon 9. A portion of the signal currents are amplified, rectified and filtered in the usual manner in the noise reduction equipment I5 and a current varying with the envelope of the signal currents is supplied to the ribbon I I. The left edge of the ribbon. Q is aligned with the centers of the apertures I, I, or slightly to the right of the centers. The right edge of the'ribbon ill 'is either mechanically adjusted or biased by the noise reduction equipment to touch the left edge of the ribbon 9, or approach closely thereto. Under the influence of the signal cur-' pf the ribbon 9.

rents the ribbon 9 oscillates alternately exposing more or less of the length or the apertures v sented by the right side of the right-hand record in Fig. 4. Similarly, the exposure of the aperture 8 produces a record of the signal currents represented by the right side of the left-hand record in Fig. 4. The two records produced by the exposure and masking of the apertures! and 8 are in phase. The ribbon I0 is moved by the currents from the noise reduction equipment tothe left an amount just suflicient to permit the free oscillation of the ribbon 9, and forms boundary lines on the left sides of the records in Fig. 4 varying with the envelope or the signal currents.

In Fig. 5 a four-ribbon light valve is shown having four ribbons, I6, ll, l8, I9. The ribbons l6 and H are connected in series by the conductor 22 and to the noise reduction equipment in place of the ribbon l0. Similarly, the ribbons l1 and ID are connected in series by the conductor 23, and to the source of signal currents in place The ribbons l6 and I1 con- {ointly control the exposure of the aperture 20, n a manner similar to the control of the aper- -tures I or 8 by the ribbons 8, I, Fig. 3, to proords in Fig. 6 are 180 degrees out of phase, that is, in push-pull relationship.' The apertures 20, 2| are vertically aligned similarly to the apertures l, 8, Fig. 3, and the images of the apertures 20, 2! are laterally aligned on the film 8 by the refractor plates 1 I, I2.

What is claimed is:

, 1. In a recording system, a source-oi light, a light sensitive medium moved at constant speed, means for controlling the light transmitted from said source to said medium comprising an opaque member having two elongated apertures displaced in the direction of movement of said medium and having their nearestshort sides in alignment and four electrically conductive ribbons suspended in a constant magnetic field and inclined to the axes of said apertures, the outer ribbons being connected in serial relationship and the inner means for supplying signal currents to the inner ribbons to move said ribbons in accordance with the instantaneous values of the signal currents, and means to supply currents derived from said signal currents to the outer ribbons to move said ribbons in accordance with the envelope of the signal currents.

2. The combination in claim 1 in which the axes of the ribbons are inclined at an angle or substantially 45 degrees to the axes of the apertures.

EMANUEL C. MAN'DERFELD. 

